Printing, the producing of hardcopy output to convey information or provide decoration, is a significant industry. Imprinting devices or printing systems such as electrophotographic, inkjet, and thermal printers deposit colorants onto receivers to produce print images. Other imprinting devices, such as facsimile (fax) machines and silver halide (AgX) printers, induce chemical changes in a receiver to cause it to develop a differential pattern of colorant on its surface, thereby providing the print image.
The colorants and receivers are examples of consumables. Consumables are stored in replaceable units (RUs, e.g., cartridges or bottles) and have a limited lifetime. When a consumable is depleted, i.e., no further supply of that consumable is available to the printer, jobs requiring that consumable can not be printed until the consumable is replenished, i.e., until more of the consumable is provided to the printer, typically by replacing the depleted RU with a full RU (new or refilled).
Providers of print services to consumers, e.g., photo developing shops, want to use as much of the consumable in each RU as possible, to save money on consumables, but do not want to run out of a consumable and therefore experience printer downtime during a period of high consumer demand.
In restaurants, partially-depleted ketchup bottles (RUs) can be combined to provide one full ketchup bottle that will satisfy a customer for the duration of his meal (avoiding running out during a demand period). However, this scheme is not generally applicable to printer consumables. Toner and ink are both difficult to handle and to clean. Inkjet RUs (ink cartridges) are highly sophisticated, and refilling one can result in the RU's becoming unable to supply any of the ink therein to the printer. Furthermore, attempting to combine consumables in two RUs can result in loss of material spilled on the floor. Furthermore, some RUs in printers are individual items with a fixed life (e.g., electrophotographic fuser rollers) and cannot be combined with others, even if partially depleted. Some consumables can be combined, such as media rolls that can be spliced together, but such operations are manual and error-prone. For example, hand-splicing of partially-depleted media rolls can increase receiver skew, result in contamination inside the printer when the splice passes through, and increase the risk of media jams in the printer (which can be time-consuming to clear, and can lead to damage in various printing systems).
Other problem domains that might seem analogous to consumable replenishment in a printer are vending machine loading, retail inventory management, and military logistics. However, these applications operate over much longer periods than printer consumable replenishments. For example, some inkjet printer cartridges can print only approximately 50 4″×6″ photographs, or approximately two rolls of film, before being depleted. In a retail photo printing environment, this would result in depletion many times per day, rather than depletion once per several days as could be the case in the problem domains listed above. This difference in time scale changes the problem qualitatively, not just quantitatively. For example, vending machines require a service technician to drive to a machine, so multiple vending machines are restocked on the same trip whenever possible. This constraint generally does not apply to the replenishing of consumables in printers.
Furthermore, restocking in a retail store does not cause downtime, unlike in a printer. Retail stores also often maintain available inventory in the back, off the shelves, from which it is readily available. The back-of-store inventory serves as a buffer to reduce the risk of depletion and unsatisfied customers; printers generally do not have such mechanisms.
Regarding vending machines, U.S. Publication No. 2008/0201241 describes an automated coffee dispenser that dynamically calculates inventory levels based on drinks served. Ingredient restocking data (dates, quantities) are loaded into the system. The system can automatically switch from empty ingredients containers to full ones. However, most printers can only hold the RUs they are actively using, and require the attention of an operator to change to a new RU when an old RU is depleted.
U.S. Pat. No. 6,980,887 describes a self-monitoring vending machine with remote network communication to provide efficient scheduling of service calls. A remote processing center calculates the capacity and velocity of the goods in the machine based on the amount dispensed. A preferred configuration of types of goods is determined to improve time efficiency between service periods for restocking of different types of goods. However, this scheme is only applicable where there is a choice of goods in the machine. Imprinting devices have consumables that are required for every job, to which different configurations are not applicable.
U.S. Pat. No. 5,608,643 describes a vending machine with a reference level sensor to determine when inventory of a product drops below a reference level that is higher than an out of stock level of the associated bin. Many printers have similar sensors to monitor their consumables. However, the scheme of '643 applies to vending machines, which operate on very different time scales than printers, as discussed above. The scheme of '643 uses the sales on past days to estimate sales on future days. This estimation cannot predict changes in sales due to special events or seasonal changes.
Commonly-assigned U.S. Pat. No. 6,370,340 describes tracking the usage of a printer using low-frequency and high-frequency sampling. This facilitates troubleshooting of the printer. Although useful, this patent does not provide consumable-replenishment schedules.
U.S. Pat. No. 7,444,088 describes a printing system with several marking engines. Print jobs are assigned to specific marking engines to balance the usage of a consumable by all the marking engines. However, this scheme does not provide any way of avoiding depletion at an undesirable time. Indeed it permits depletion to occur at the same time on multiple printers, increasing the likelihood that one marking engine will be unable to serve as a backup for another.
These schemes describe various ways of load-balancing and replenishing or restocking, but do not take into account the time scale of printer operation and the constraints on consumables in printers. There is a continuing need, therefore, for a way of managing consumables in a printer, to use as much of the consumable in each RU as possible without running out of a consumable during a period of high consumer demand.